utils: fix build error with g++

g++ does not support __builtin_choose_expr, so we can't support
byte swapping as constant expression there.

Reported-by: Cleynhens Stijn <Stijn.Cleynhens@technicolor.com>
Signed-off-by: Felix Fietkau <nbd@nbd.name>

diff --git a/utils.h b/utils.h
index b64b400..019d817 100644 (file)
--- a/utils.h
+++ b/utils.h
@@ -127,9 +127,18 @@ int clock_gettime(int type, struct timespec *tv);
 #define __eval_once(func, x)                                           \
        ({ __typeof__(x) __x = x; func(__x); })
 
+#ifdef __cplusplus
+/*
+ * g++ does not support __builtin_choose_expr, so always use __eval_once.
+ * Unfortunately this means that the byte order functions can't be used
+ * as a constant expression anymore
+ */
+#define __eval_safe(func, x) __eval_once(func, x)
+#else
 #define __eval_safe(func, x)                                           \
        __builtin_choose_expr(__is_constant(x),                         \
                              func(x), __eval_once(func, x))
+#endif
 
 #if __BYTE_ORDER == __LITTLE_ENDIAN